Book at award, not at mobilisation
The moment the project is awarded, lock in accommodation. Waiting until mobilisation means competing with other crews for the same beds. Even speculative bookings (with reasonable cancellation terms) are worth it.
Reserve buffer capacity
A 12-person crew needs at least 14 beds booked. People get sick, replacements arrive, scope changes. Slightly over-booking and releasing late is cheaper than scrambling for emergency accommodation mid-project.
One source of truth
Stop having multiple PMs book accommodation independently. One coordinator, one supplier (TNS or otherwise), one invoice. Saves 5-10 hours/week of admin on a large project.